1. FIELD OF THE INVENTION
The present invention relates to devices for testing heat sensing units to determine if such units are operating within specified temperature ranges.
2. DESCRIPTION OF THE PRIOR ART
Internal combustion locomotive engines are provided with heated sensing units disposed in the water circulation system for cooling of such engines. Generally a plurality of such thermostats are provided, e.g. four thermostats, to sense temperatures within the cooling system of 170.degree. F., 180.degree. F., 194.degree. F., and 215.degree. F., respectively, and to provide a signal when such respective temperatures are exceeded; or three thermostats to sense temperatures of 170.degree. F., 194.degree. F. and 215.degree. F., respectively. These provide a signal when such respective temperatures are exceeded, and also if there is accidental engine breakdown on the railway line. It is manifest that the accuracy of such thermostats and the true operation thereof is important to prevent damage to the engine.
In the past, such testing of the thermostats has taken place by actual running of the locomotive engines. Since the capacity of the water cooling system is of the order of 200 gallons, such tests required from 1 to 4 hours to complete, depending on ambient temperature. It is clear that this testing means is very wasteful.
Analogous arts have proposed devices for testing of heat detecting devices. For example, U.S. Pat. No. 2,653,470 patented Sept. 29, 1953 by M. Couper provided an apparatus for the testing of conventional radiator valves which included a boiler having an electrical heating unit at the bottom, a pressure indicator at the top and a special construction at the top to hold the radiator valve being tested rigidly in connection with a receiving head and over a funnel. A relief valve is mounted in the upper end of the boiler and electrical connection is provided for the heating element.
U.S. Pat. No. 2,729,095 patented Jan. 3, 1956 by E. M. Greer provided test equipment to test oil temperature regulating valve assemblies. These valve assemblies are disposed in the oil recirculating system of engines and serve to counteract the effect of the circulation of oil which is too hot or too cold. In the past, whether the valves operated correctly at low and high temperatures were simulated by means of test equipment on which the temperature regulating valve unit is mounted. The patented device relied on the use of both oil heating and oil cooling units in an oil reservoir, with a test pad for mounting the valves to be tested in contact with the circulating oil.
U.S. Pat. No. 2,854,844 patented Oct. 7, 1958 by Howell provided a portable probe having a capacity of chamber into which the unit to be tested could be inserted. A heating means was provided in the probe and also a local heat detecting means, whereby the output of the local heat detecting means in the probe could be compared to the indicating equipment permanently wired to the unit under test.
U.S. Pat. No. 3,067,604 patented Dec. 11, 1962 by R. D. Brunson provided an improvement in the aforesaid Howell U.S. Patent by the discovery that selective attenuation of the signal from the heat detecting electrical means in the probe permits use of a given probe with a variety of different designs of units to be tested. Thus, if the signal from the local heat detecting means is attenuated or modified for the distinct unit under test than a correspondence between the local temperature reading and the unit's own reading may be reestablished.
Finally, U.S. Pat. No. 3,347,085 patented Oct. 17, 1967 by S. F. Harris provided apparatus for the testing of thermostat devices particularly those associated with electrical water heaters. The patented device included a container provided both with electrical heating means and insulated housing means for removably receiving the thermostats. It also included a temperature indicating probe control means intermittently energizing the electrical heating means, and indicators were connected to the thermostats to indicate whether the selected thermostat responded to an adjustment of the temperature to a measured preselected temperature.